An eccentric-worm pump generally is supplied with bulk material to be displaced by the pump, e.g. granular solids, viscous materials such as sewage sludge, and other flowable materials which are susceptible to bridging, with a feeder which may have a generally rectangular plan funnel structure which is provided above a trough in which a feed worm is disposed, advancing the material axially into the housing of the eccentric worm pump which can be of the Moineau-pump type.
Above the feed worm in the funnel, a pair of bridge breaker shafts can be provided and the shafts can have paddles whose outer ends define orbits around the axes of the breaker shafts which overlap in axial direction, i.e. the radial paddles of the two breaker shafts interdigitate.
The purpose of the breaker unit formed by the breaker shafts and their respective paddles is to prevent the formation of bridges of the bulk material to be displaced in the funnel across the downwardly converging walls thereof above the feeder shaft, such bridging tending to impede the continuity of flow of the bulk material downwardly through the funnel.
Such systems have been found to be highly effective where the bulk material, was, for example, sludge, especially activated sludge from the clarifiers of sewage-treatment plants, sludge from fermentation basins or the like. Usually such sludges, before being displaced with such pumps are subjected to a preliminary drying on so-called belt dryers or vacuum-belt dryers.
The feed worm and the bridge-breaker shafts generally are driven at speeds between 30 and 150 R.P.M., which speeds may be variable so that an optimum speed can be selected for the particular material displaced. The eccentric-worm pump is usually flanged by its eccentric to the worm shaft.
A system of this type is described in German Utility Model application DE-GM No. 85 21 574.
While the paddles have been found to be highly effective in preventing bridge formation or breaking any bridges which do form, especially when the bridge-breaker shafts are counter-rotating, i.e. are driven in opposite senses of rotation and have their paddles axially offset from one another from shaft to shaft to enable the respective orbits to overlap as described, it has nevertheless been found that it is possible to improve upon the efficiency of such feeders.